The rapid and accurate detection of target molecules is critical for many areas of research and medical diagnosis. Important features for a diagnostic technique to be used for the detection of analytes are specificity, speed, and sensitivity. Time constraints and ease of on-site analysis can be major limitations.
Since its discovery in 1987 (Palmer, R. M. J. et al., 1987, Nature, 327:524-527), nitric oxide (NO) has been implicated in disparate pathologies including: metastasis of cancerous cells (Anbar, M. and Gran, B. M. 1997, Journal of Pain and Symptom Management, 14:225-254), inflammation in the airway of an asthmatic (Batra, J. al., 2007, Thorax, 62:16-22.), onset of hypercholesterolemia, atherosclerosis, and hypertension diseases (Gibaldi, M. 1993, J. Clin. Pharmacol., 33:488-496; Star, R. A. 1993, Am. J. Med. Sci., 306:348-358; Tanner et al., 1993, Sem. Thrombosis Hemostasis, 19:167-175), massive infection and septic shock, and regulation of wound healing.
Generation of nitric oxide by naturally occurring, endogenous, processes has been demonstrated by several studies to correlate with wound healing (Schäffer, M. R. et al., 1996, Journal of Surgical Research, 63:237-240; Witte, M. B. and Barbul, A. 2002, The American Journal of Surgery, 183:406-412). Briefly, wound collagen accumulation can be stimulated by arginine and, during wound healing, nitric oxide is produced from oxidation of L-arginine by a family of enzymes known as nitric oxide synthases. Conversely, low levels of nitric oxide generation indicate a delayed or inhibited healing response, which is often associated with chronic, non-healing wounds.
Unfortunately, direct measurement of nitric oxide is difficult due to its half-life in vivo of only a few seconds or less. Therefore, stable nitric oxide metabolites, nitrite (NO2−) and nitrate (NO3−), are widely used as surrogates for indirect determination of nitric oxide in biological fluids. Nitric oxide metabolites are currently measured using time and labor intensive techniques (e.g., the Griess reaction) that also require expensive equipment (e.g., spectrophotometer, fluorometer, and/or plate reader). Thus, rapid, point-of-care diagnostic methods and devices for nitric oxide are needed.